The study is being conducted at University Clinic of Pulmonary and Allergic Diseases Golnik, Slovenia. Patients with suspicion of acute exacerbation of COPD will be screened at admission when they will be informed about study details. After explanations of concerns and questions that they might have, a signed informed consent will be collected. During 48 hours, patients will be included according to their eligibility. Main inclusion criteria are COPD stage II-IV according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, ability to perform phone contacts and availability for home visits. Patients will be excluded if in unstable or terminal stage of disease other than COPD, if they will die during hospitalization, or if unable to follow the study protocol.